UNSPECIFIED (2002) Nitrogen stress response of Prochlorococcus strain PCC 9511 (Oxyphotobacteria) involves contrasting regulation of ntca and amt1. JOURNAL OF PHYCOLOGY, 38 (6). pp. 1113-1124. ISSN 0022-3646

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Abstract

The ntcA and amt1 genes (encoding a transcriptional activator of genes involved in nitrogen metabolism and a high affinity ammonium transporter respectively) from the axenic Prochlorococcus strain PCC 9511 were amplified, cloned, and sequenced. Cultures of this strain were exposed to nitrogen deprivation, and the expression of ntcA and amt1 was monitored along with cell density, photochemical quantum yield (as determined from F-v /F-m measurements), and cellular C:N ratios. Nitrogen deprivation led to arrested cell growth, reduced photochemical quantum yields, and increased cellular C:N ratios. Surprisingly, transcript accumulation patterns of ntcA and amt1 were not correlated. High levels of amt1 transcript were observed in both nitrogen-replete and -deplete conditions. Expression of amt1 declined under severe deprivation of either phosphorus or nitrogen and showed a positive correlation with photochemical quantum yield. In contrast, ntcA expression was specifically enhanced in the absence of ammonium. High ntcA transcript levels were maintained over time and did not decline with low F-v /F-m values under severe N deprivation. Although ntcA transcript levels correlated somewhat with cellular C:N ratios, at the onset of nitrogen deprivation increases in ntcA mRNA levels occurred before increases in cellular C:N ratios. Constitutively high ammonium transporter expression together with low cellular ammonium requirements are likely to have important implications for the success of Prochlorococcus in the nitrogen-poor oligotrophic waters where they are most abundant. The function of NtcA in Prochlorococcus strain PCC 9511 remains unclear.

Item Type:	Journal Article
Subjects:	S Agriculture > SB Plant culture Q Science > QH Natural history > QH301 Biology
Journal or Publication Title:	JOURNAL OF PHYCOLOGY
Publisher:	BLACKWELL PUBLISHING INC
ISSN:	0022-3646
Date:	December 2002
Volume:	38
Number:	6
Number of Pages:	12
Page Range:	pp. 1113-1124
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/10198

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